'Appointed Time' in the Bible

“The sons of Israel are to keep the Passover at its appointed time.

On the fourteenth day of this month at twilight, you shall keep it at its appointed time; according to all its statutes and ordinances you shall keep it.”

Those men said to Moses, “We are [ceremonially] unclean because of [touching] a dead body. Why are we being restrained from presenting the Lord’s offering at its appointed time among the Israelites?”

But the man who is [ceremonially] clean and is not on a journey, and yet does not observe the Passover, that person shall be cut off from among his people [excluding him from the atonement made for them] because he did not bring the Lord’s offering at its appointed time; that man will bear [the penalty of] his sin.